I just cleaned and reoiled mine, and I have an ever so slight whistle coming from the engine bay consistent with acceleration. Nothing anyone else would notice, but it's driving me crazy. I refitted the filter, but I'm still getting the whistle. I may just buy a new filter.
I don't mean to thread jack - I love this product.
MCS 1WNR with 600/900 spring rates / Vorshlag camber plates / Apex ARC-8s with Apex studs / NT-01s / Stoptech Trophy ST-60/ST-40 / UUC Corsa axle-back with Fabspeed HFC and x-pipe / Schroth Quick Fit Pros / HANS Sport II / AA green filter / CSF Radiator (not installed on current car)